1. Field of the Invention
The present invention relates to an optical device for splitting up a multi-wavelength light beam into a plurality of individual beams each comprising light of a different wavelength or a narrow band of wavelengths. Such a device is commonly called a de-multiplexer.
2. Background of the Related Art
It is known to use an optical transmission grating to split up a multi-wavelength beam of light into individual beams of light of different wavelengths or narrow bands of wavelengths. Such a device comprises a first optical system, for example, a mirror, for directing the multi-wavelength beam onto the grating. On passing through the grating, the multi-wavelength beam is split into individual beams of light of different wavelengths or narrow bands of wavelengths, with the individual beams emerging from the grating at different angles. The individual beams are passed to a second optical system, for example, another mirror, which directs each individual beam into a respective individual waveguide or other optical path device. In such a device, the light passes through each of the two optical systems once and the grating once.
It is also known to use an optical reflection grating formed on the surface of a mirror to split up a multi-wavelength beam of light.